In the liquid crystal display device, voltages are applied between pixel electrodes and a common electrode, thereby changing the orientation direction (i.e., the longitudinal direction) of liquid crystal molecules, so that an image is displayed on a liquid crystal panel while the amount of light to be transmitted through a liquid crystal layer is controlled.
However, to change the orientation direction of liquid crystal molecules in accordance with the applied voltage, it takes a predetermined period of time after the application of the voltage. For example, in the case of a widely used TN (Twisted Nematic), IPS (In-Plane Switching), FFS (Fringe Field Switching), or VA (Vertically Aligned) liquid crystal display device, it might take a time period of about 50 milliseconds after voltage application to the liquid crystal layer until the orientation direction of liquid crystal molecules changes. In addition, the response speed of the liquid crystal changes in accordance with the temperature, and the response speed decreases as the temperature lowers. Moreover, in the case where the image refresh rate is 60 Hz, one frame period is 16.7 milliseconds. Accordingly, if the response period of the liquid crystal becomes longer than 16.7 milliseconds, image lag might occur on the screen, resulting in reduced display quality. Note that one frame period for a refresh rate of 60 Hz will also be referred to herein as a “normal frame period”. Accordingly, the duration of a normal frame period is 16.7 milliseconds.
Therefore, to improve the display speed of the liquid crystal display device, for example, Japanese Laid-Open Patent Publication No. 2004-4629 discloses a liquid crystal display device in which “overshoot drive” is performed to apply a higher voltage to a liquid crystal layer than a voltage corresponding to an image signal. In the overshoot drive, a look-up table (referred to below as an “LUT” or a “table”) is used in which correction values are stored and correlated with their respective combinations of grayscale values for the previous and current frames. More specifically, a correction value correlated with a combination of grayscale values for the previous and current frames is read from the LUT, and overshoot drive is performed using a correction image signal obtained by correcting an image signal with the correction value. As a result, it is rendered possible to improve the response speed of the liquid crystal display device.